Robots Unlimited: Life in a Virtual Age by David Levy

Author:David Levy [Levy, David]
Language: eng
Format: epub, pdf
Tags: Computers, Machine Theory, Mathematics, Recreations & Games, Technology & Engineering, Robotics, Automation, History & Philosophy
ISBN: 9781568812397
Google: KcfCYC9Z8ysC
Amazon: B003L77FV6
Publisher: Taylor & Francis
Published: 2005-08-30T00:00:00+00:00

to recognize the most recently presented pattern every time, but all the

other patterns never.

The Creativity Machine

A remarkable and highly original application for ANNs has been devised

by Steve Thaler, a physicist turned AI-researcher. During the late 1980s

25The strengths may be thought of as measures of how important it is, in a particular classification task, that some combination of two or more different inputs are present simultaneously.

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How Computers Think

and early 1990s Thaler had the idea of investigating what would happen

to an ANN if he tried to “kill” it by randomly degrading the weights con-

necting the artificial neurons. He trained a network, then held its input

information constant and observed what happened to the output, while,

one by one, he switched off the network’s connections or reduced their

strength at random—the computer equivalent of killing individual con-

nections between the neurons in a human brain. Intuitively one would

expect this to have the effect of completely destroying the performance

of the network, but instead the stunted versions were not incapable, they

merely performed differently.

The changes in the internal state of Thaler’s network were interpreted

as though they were caused by changes in the input information rather

than by the death of some of its neurons, and the network made a stab

at what the outputs might be, much as a human might guess a word that

has letters missing. Thaler discovered that, as the neurons “died”, the

network generated memories, then fragments of memories, and finally

new concepts created from fragments of memories. He also found that

an ANN will respond in the same way if, instead of deleting connec-

tions, he simply changed some of their weights. His first breakthrough

came on Christmas Eve in 1989, when he typed the lyrics of some of his

favourite Christmas carols into an ANN. Once the network had learned

these songs he started to switch off its connections. Gradually the net-

work “began to hallucinate”, creating new ideas in the process. As it was

degrading, the network dreamed up new carols, each of which was cre-

ated from shards of its broken memories. One of its final creations was

the line “All men go to good earth in one eternal silent night.” What

most intrigued Thaler about the program’s dying gasps was how creative

the process of dying could be. This prompted the idea: “What if I don’t

cut the connections, but just perturb them a little?” [4]

Thaler tried “tickling” a few of the connections in the network, a

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